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HP 50g & SD Cards: Performance, Format, Notes
07-21-2016, 07:49 PM (This post was last modified: 07-22-2016 08:20 AM by matthiaspaul.)
Post: #29
RE: HP 50g & SD Cards: Performance, Format, Notes
(07-21-2016 05:07 PM)Joe Horn Wrote:  except the 2GB card when formatted FAT32, which takes roughly 2 seconds to turn on.
This delay is most probably caused by an incomplete FAT32 implementation in the HP 50g.

Many FAT32 implementations for embedded systems ignore, misinterpret, or don't properly maintain the contents of the "FAT32 filesystem info sector", which contains a "free data clusters" entry at offset +1E8h and a "most recently allocated cluster" entry at offset +1ECh. These entries specifically exist to speed up seeks on FAT32 volumes. Misinterpretion (ignoring these values when they are valid or trusting them when they are invalid) can happen if the implementation does not properly handle the "media mount flag" (bit 0 at offset +36h in a FAT32 EBPB) or the "volume mount flag" (bit 27 in the FAT32 cluster 1 entry) during startup (mount), shutdown (unmount), or media change (unmount/mount).

Unfortunately, if that would turn out to be the case with the 50g, we could do nothing to "fix" it...



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RE: HP 50g & SD Cards: Performance, Format, Notes - matthiaspaul - 07-21-2016 07:49 PM

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